The present invention relates to battery monitors and, more particularly, to a battery monitor that incorporates a software trim.
In order for portable electronic devices to operate properly, they generally require a portable power source, which is typically provided in the form of batteries. Each battery type has its own discharge characteristics that depend on the load characteristics it operates under. In order to provide reliable operation of the portable device, it is often desirable to monitor the battery's charge level to assure that the charge is sufficient to reliably operate the portable electronic device. In the event the charge level of the battery falls below a certain level, or levels, it may be desirable to warn the user that the battery requires recharging. Further, when the battery falls below a critical level, it is desirable to stop all operations of the portable electronic device to prevent undesirable operations. This situation is particularly evident when the portable devise operates as a portable telephone or radio which, in uncertain operating condition, may disseminate undesirable electromagnetic radiation.
Prior battery monitors have typically been external devices to integrated circuits in portable electronic devices. Those external battery monitors have required inclusion of additional components on the system board, as well as additional external pins on the integrated circuit. Those requirements increase the amount of board space necessary to accommodate the components and pins. The required additional board space, components, and external pins increases expense of the devices. These requirements are particularly undesirable with the now increasing demands for miniaturization and decreased cost.
The prior battery monitors have also typically varied widely in the accuracy of charge detection achieved by the monitors. It is desirable to accurately detect battery charge level, for example, to enable longer and more accurate usage of portable electronic devices. In the conventional battery monitors, fuse pads on the periphery of the battery monitor's integrated circuit have allowed for accuracy adjustment. In particular, each battery monitor has been individually testable for accuracy and adjustable by means of "blowing" or opening predetermined fuse pads on the battery monitor's periphery. This practice has resulted, however, in a number of problems. For example, the fuse pads consume space on the battery monitor's periphery which could otherwise be used for other functions. Moreover, it is possible for the opened fuse pads to become shorted out or corroded during operations, thus causing the battery monitor to return to its original state.
In order for digital integrated circuits to operate properly, it is generally necessary to first cause the circuitry of the integrated circuit to start from a known state, before it performs other operations. Once the circuitry is in the known state, operations of the circuitry can then be conducted in an orderly and predictable fashion. Typically, this known state is called the reset state. According to particular design, the reset state may occur, for example, when power is first is applied to the integrated circuit. Design may also cause the integrated circuit to be reset to the reset state while power is applied during operations for various reasons. In certain applications it is also desirable that the integrated circuit monitor various internal and external conditions and that the integrated circuit reset to the state if any of those conditions are not as expected for desired operation or raise questions about that operation.
One internal condition that may be, and frequently is , monitored for the aforementioned reasons is selected operational states of a microcontroller or other integrated circuits that execute instructions, such as microcode, firmware or software, incorporated in the integrated circuit. For appropriate operation of the integrated circuit the microcontroller must process instructions in an orderly fashion. It may happen, from time to time, that, through inadvertent efforts in the instructions or circuitry, other unforeseen events, or even other occurrences, the microcontroller or software controlling it operates in an unexpected or undesirable manner. When this occurs, it is in the many instances desirable to reset the integrated circuit before allowing the microcontroller or software to resume normal operations.
In instances in which an integrated circuit is powered by a battery or other depleting power source, an external condition that may be monitored is the charge level in the battery. Monitoring the battery's charge level may be desirable because once the charge falls below a certain level, it may be hard, if not impossible, to predict the operation of the integrated circuit. In order to avoid the uncertainly in those cases, it may be desirable to cause the integrated circuit, or portions of it, to maintain a particular state or even shutdown when the charge level of the battery or other power source has depleted to a critical level.
The unpredictability of an integrated circuit powered by a battery having a low charge, or whose software is not operating properly is of particular concern when the integrated circuit operates to control a wireless communication device, such as a portable phone or radio. This concern arises because of the need to prevent the device from sending out undesirable electromagnetic signals.
Heretofore, integrated circuits have utilized external battery monitors which have necessitated additional components on the system board as well as additional external pins on the integrated circuit. This has resulted in increased board space and greater expense, both of which conditions are undesirable with the increased need for miniaturization and decreased cost.
What is needed, therefore is a battery monitor arrangement that addresses the above identified problems. The present invention provides these and other advances and improvements in the technology and art.